This application claims the priority of German application 198 42 979.7, filed in Germany on Sep. 19, 1998, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a vehicle seat of the generic type having a seat heating arrangement integrated into a seat cushion, a ventilation device for ventilation of the cushion and a control unit for controlling the heating arrangement and ventilation device.
In the case of a known vehicle seat of this type (German Patent Document DE 196 28 698 C1), the cushion has a ventilation layer which consists of a coarse-meshed knitted spacing fabric, rests on a cushion support consisting of rubberized hair or foam and is covered by an air-permeable pressure-distributing layer. A covering filling consisting of a nonwoven fabric, wool batting or a foam layer of approximately 5-8 mm in thickness is positioned between the pressure-distributing layer and a cushion covering which covers the cushion surface, the cushion covering and covering filling likewise being of air-permeable design. Electric heating wires of the seat-heating arrangement are positioned between the pressure-distributing layer and the covering filling. A arranged in air channels made in the cushion support are miniature fans of the ventilation device which take in air at the underside of the seat and blow it into the ventilation layer. The air spreads out over a large surface area in the ventilation layer and flows out, via the air-permeable cushion layers, at the seat surface and cools the cushion here, which has been heated for example by insolation, to comfortable temperatures. When the seat is occupied, the ventilation of the cushion prevents heat from accumulating in the occupied seat surface and dissipates perspiration moisture from the seat surface.
In the case of a likewise known vehicle with a seat-heating arrangement and seat-ventilation device U.S. Pat. No. 5,934,748 which claims priority to (German Patent Document DE 197 03 516 C1), a control unit is provided in order to achieve considerable temperature-conditioned seat comfort which prevents the seat occupant from perspiring and also from becoming too cold, and said control unit is connected, on the inlet side, to a temperature sensor integrated in the cushion and, on the outlet side, to the electric circuits of the seat-heating arrangement and seat-ventilation device. The control unit controls the switching on and switching off of the seat-heating arrangement and seat-ventilation device, in dependence on the cushion-surface temperature measured by the temperature sensor, in accordance with a predetermined control algorithm.
Such seat-heating arrangements react extremely sluggishly when switched on since the heating elements are located beneath the covering filling or lamination, and in the case of leather seats the heating up is made more difficult by the poor heat conduction of the leather covering. In the winter in particular, a delay in the response time, which may last up to 3 minutes, of the seat-heating arrangement is disadvantageous.
An object of the invention, in the case of a vehicle seat of the type mentioned in the introduction, is significantly to shorten the response times of the seat-heating arrangement when the latter is switched on.
The object is achieved according to the invention by providing an arrangement wherein the control unit at least temporarily activates the ventilation device immediately after the seat-heating arrangement is switched on.
The vehicle seat according to the invention has the advantage that the specific combination of the seat-ventilation device with the seat-heating arrangement in the heating-up phase doubles the heating-up speed of the cushion because, by virtue of the seat-ventilation device being switched on, the ventilation taking place uniformly and over a large surface area, the warm air, which circulates around the heating wires as soon as the seat-heating arrangement has been switched on, is forced to the seat surface.
Advantageous features of preferred embodiments of the vehicle seat according to the invention with expedient configurations and developments of the invention are described herein and in the claims.
According to a preferred embodiment of the invention, the control operation, in the control unit, which causes the seat-heating arrangement to be switched on is such that the seat-heating arrangement and ventilation device are switched on at full power and the power of the ventilation device is reduced asymptotically to a predetermined end value within a predetermined time interval. This co-ordination of the heating and ventilation power achieves an optimum heating-up speed. This means that the end value can be predetermined manually depending on how warm the user is feeling.
Alternatively, according to one embodiment of the invention, the end value is fixed and, when the end value is reached, the control unit controls the seat-heating arrangement and the ventilation device, in dependence on the cushion-surface temperature measured by means of a temperature sensor, in accordance with a predetermined control mode.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.